1. Field of Invention
This invention relates generally to hybrid vehicles and more particularly to managing power in a hybrid vehicle having an engine, an electric motor, and an energy storage element coupled to the motor.
2. Description of Related Art
Hybrid electric vehicles having an engine (such as an internal combustion engine) and an electric motor, for providing power to the vehicle have become a viable alternative to conventional internal combustion engine vehicles. While such vehicles may require more complex power transmission components, this complexity is offset by improved fuel consumption and a corresponding reduction in emissions of pollutants from the engine.
Given the present climate of higher prices for fossil fuels, there is a corresponding desire to further reduce fuel consumption costs when operating hybrid vehicles. Hybrid electrical vehicles reduce fuel consumption by apportioning the power required to operate the vehicle between the engine and electric motor, to cause these components to operate at efficient operating points. For example, when moving slowly or when starting off from a stationary position, the electric motor may be considerably more efficient than the engine and in this case most of the power may be supplied by the motor. At higher speeds, where engine efficiency is better, a greater proportion of power may be supplied by the engine. Accordingly, the management of power distribution between the engine and the motor for a hybrid electric vehicle is an important factor in achieving the best overall efficiency, low fuel consumption, and minimizing operating costs. There remains a need for improved methods and apparatus for managing power in a hybrid vehicle.